The invention relates to a connection element for the captive mounting of a lever-type cam follower, which is used to actuate a gas-exchange valve of an internal combustion engine, onto a support element with a spherical end. The cam follower is pivotably mounted on the spherical end via a concave molding. Here, the connection element made from flat material is arranged, with a central section, on a lower side of a base, which is oriented towards the support element. This base surrounds the concave molding and connects to side walls of the cam follower. The connection element forms, with two limbs spaced apart at a distance from each other and also a web connecting these limbs, a U-shaped recess, which extends in a longitudinal direction of the cam follower and which surrounds a ring-shaped groove below the spherical end in a fork-like manner.
In a known way, such connection elements allow the generation of a component, which includes, for example, a finger lever as a cam follower and a support element. Such a component then minimizes the risk of potentially incorrect assembly by the customer. Among other things, this could consist in the finger lever being mounted rotated by 180° in the valve train. In this case, the contact partners of the spherical head of the support element and the spherical cap of the finger lever and also the valve shaft end and the corresponding counter surface on the finger lever being interchanged. Such an incorrect assembly would lead at least to incorrect functioning of the valve train and even, in the worst case, to serious engine damage. Additional requirements on this connection element consist in that, on one side, a separation of the finger lever and support element due to transport effects is reliably ruled out and, on the other side, the connection element does not contribute disadvantageously to valve-drive wear in the pivoting motion of the finger lever on the support element.
In DE 196 17 523 C2, different variants of a connection element satisfying the requirements noted above are proposed. This connection element engages in the ring-shaped groove below the spherical end for captive connection of the finger lever and support element. The material thickness of the connection element is matched to a width of the groove, so that it can move freely in the groove into every pivoting position of the finger lever. Thus, the finger lever can execute a pivoting motion in the actuation direction of the gas-exchange valve, which is not impaired by frictional effects of the connection element. In one of these variants according to the FIGS. 3 and 4 of the mentioned publication, the connection element is made of flat material and surrounds the finger lever at the concave molding in a U-shaped configuration with two limbs oriented in the direction of the gas-exchange valve. At their end, these limbs transition into retaining lugs, which snap behind the material surrounding the concave molding for fixing the connection element in the longitudinal direction of the finger lever. Furthermore, in this variant, the limbs form a U-shaped recess and surround the annular groove in a fork-like manner. The U-shaped recess is here embodied open towards the gas-exchange valve.
In general, in the assembly of the finger lever with the support element, it is typical to clip the spherical end of the support element behind a recess of the connection element engaging in the groove. In this way, the connection element is already mounted on the finger lever. Such an assembly process is now also possible and is to be performed only using these means for the previously mentioned variants of the cited publication. This is based on the condition that pushing the connection element in the longitudinal direction onto the finger lever is not possible for a spherical end of the support element held in the concave molding, because the retaining lugs necessary for attachment spread out the lower limb of the connection element before reaching the end position and would collide with the piston periphery of the support element below the annular groove.
A prerequisite for trouble-free clipping of the support element behind the recess of the connection element is now its elastic deformation in the area of the recess. The necessary elasticity can be achieved without a problem through the suitable geometry of the recess and also suitable properties and thickness of the connection element material. Nevertheless, a mounting gap remains perpendicular to the actuation direction of the finger lever between the connection element and the annular groove in the support element. Consequently, the finger lever is also not completely hindered by the connection element for a pivoting motion perpendicular to its actuation direction, wherein this pivoting motion can then equal up to 15°. Such tipping of the finger lever about its longitudinal axis can also occur when it is mounted in the internal combustion engine, namely if there is a loss of contact between the finger lever and the actuating cam. Causes for such a loss of contact can be an undesired lowering of the usual support element with hydraulic lash compensation or jumping of the finger lever from the actuated cam as a result of overspeed in the internal combustion engine.
In this respect, in particular, finger levers with very narrow cam contact surfaces are to be considered. These can be used in installation space-limited multi-valve engines or also in variable valve controllers, in which a cam arrangement comprising several cams of different stroke is mounted so that it can be displaced axially on its camshaft and is brought into engagement with the finger lever by the one cam matching the operating state of the internal combustion engine. The finger lever is then especially at risk in terms of further or complete tipping of the support element, because it may no longer be sufficiently aligned with the cam due to the narrow cam contact surface when contact to its cam is restored.